Spinopelvic Parameters in the Elderly: Does Inadequate Correction Portend Worse Outcomes?

Introduction: This study aimed to compare the outcomes of corrective fusion for adult spinal deformity (ASD) in older people using two different sagittal correction goals: the conventional formula of "pelvic incidence (PI)-lumbar lordosis (LL) mismatch <10°" and an undercorrection strategy based on the range of 10°≤PI-LL≤20°. Methods: A total of 102 consecutive patients (11 male and 91 female patients; mean age, 72.0 years) aged above 65 years with scoliosis >20° or LL<20° who had undergone long-segment fusion from the lower thoracic spine to the pelvis for ASD and had been followed-up for a minimum of two years at our institution since March 2013 were included in this retrospective study. After excluding patients with PI-LL≤-10° on postoperative standing radiographs, the remaining patients were divided into two groups: 31 patients with 10°≤PI-LL≤20° (U group) and 63 patients with -10°<PI-LL<10° (M group). Radiological and clinical outcomes were compared between the groups. Results: The incidence of proximal junctional kyphosis and mechanical failure was not significantly different between the groups (p=0.659 and 1.000, respectively). After excluding patients who underwent reoperation due to mechanical failure, there were no differences in the Oswestry Disability Index (ODI) and each domain of the Visual Analog Scale score, Scoliosis Research Society-22r patient questionnaire (SRS-22r), or the short form 36 health survey questionnaire at the final observation between the U (n=27) and M (n=57) groups. In addition, the non-inferiority and equivalence of the U group to the M group were demonstrated in all domains of the SRS-22r and ODI. Furthermore, the superiority of the U group was demonstrated by the functional domain of SRS-22r. Conclusions: For the sagittal correction goal in corrective fusion surgery for ASD in the elderly, strict adherence to "PI-LL mismatch <10°" is not necessary and "PI-LL≤20°" may be acceptable.